In a conventional air-outlet mode selecting device of a vehicle air conditioner, a face opening, a defroster opening and a foot opening of an air conditioning unit are opened and closed by the use of a single rotary door having an outer peripheral door surface turning with a rotary shaft. Further, the outer peripheral door surface turning with the rotary shaft is arranged at a position separated by a predetermined distance outward in a radial direction from the center of the rotary shaft. This outer peripheral door surface is usually shaped like an arc having its center at the rotary shaft. However, in this air-outlet mode selecting device, all of the face opening, the defroster opening and the foot opening need to be arranged in an arc shape along the turning path of the outer peripheral door surface of the rotary door. On the other hand, the air conditioning unit is arranged in a place that is inside a dashboard of the vehicle and is subjected to extreme spatial constraint. Thus, it is difficult to perform the arrangement of three air outlet openings of the face opening, the defroster opening and the foot opening in the shape of an arc.
Further, in order to ensure the respective air volumes blown off from the three air outlet openings, the areas of the respective air outlet openings need to be enlarged and hence the area of the outer peripheral door surface of the rotary door needs to be enlarged. As a result, it is difficult to arrange the air outlet openings, the rotary door is increased in size, and door operating force is increased.